1. Field of the Invention
The present invention relates to a start control apparatus and a program for a start control method.
2. Description of the Related Art
In the related art, for example in a vehicle equipped with a vehicle drive apparatus (power train) such as a stepped automatic transmission, a continuously variable automatic transmission (CVT), a semi-automatic transmission, an electrically driven apparatus using a drive motor as a drive source, and an electrically driven apparatus using a drive motor, an engine and a power generator as drive sources, when a range is selected by positioning of a shift lever (or other shift control member), a vehicle drive control apparatus for controlling the vehicle drive apparatus turns on and off solenoids or the like in accordance with the transmission logic for the selected range. For this purpose, a position determination apparatus is provided. The position determination apparatus receives an output signal from a position sensor. The position determination apparatus determines the shift position, i.e., position of the shift lever, based on the output signal to detect the selected range.
The position sensor may be a non-contact sensor having a magnet and a Hall IC or the like. When the shift lever or the like is repositioned by the driver, a manual shaft and the magnet attached to the manual shaft are rotated together responsive to the movement of the shift lever. The Hall IC generates an analog sensor output corresponding to the rotation of the magnet. For example, see Japanese Patent Application Laid-Open No. 2001-174212.
For example, in a vehicle equipped with a stepped automatic transmission, a start control apparatus is provided. When it is determined that a range suitable for starting the engine, i.e., an engine start range such as the parking range or the neutral range, is selected in order to start the engine, the start control apparatus outputs a start permission signal to a motor drive circuit to permit operation of the starter motor. As a result, the motor drive circuit starts the starter motor by supplying electrical current to the starter motor, and the starter motor, in turn, drives the engine.
However, in the start control apparatus of the related art, when the starter cable, i.e., the power line for supplying electrical current to the starter motor, is run near the position sensor, the magnetic field generated by the electrical current flowing through the starter cable in operation of the starter motor may affect the Hall IC, and cause errors in the sensor output of the Hall IC.
As a result, even if the shift lever is actually in a position selecting an engine start range, it may be erroneously determined that an engine start range has not been selected due to error in the sensor output of the Hall IC, the loss of performance in the Hall IC, or the like. In this case, the start of the starter motor is prohibited unintentionally.
FIG. 2 is a time chart showing operation of the start control apparatus in the related art wherein Vh denotes a voltage value indicating the sensor output of the Hall IC. When the voltage value Vh is in a permission region, i.e., not less than a lower limit value VNL, the start control apparatus permits the start of the starter motor. When the voltage value Vh is less than the lower limit value VNL, i.e., in a prohibition region, the start control apparatus prohibits energizing the starter motor.
That is, when the shift lever is in a position corresponding to an engine start range, e.g., in the neutral position, the voltage value Vh (the sensor voltage expressed in volts [v]) is not less than the lower limit value VNL. Therefore, the start control apparatus permits operation of the starter motor. However, a magnetic field is generated when electrical current flows through a line to the starter motor at time t1, and the magnetic field affects the Hall IC. When the voltage value Vh becomes less than the lower limit value VNL at time t2, the start control apparatus prohibits operation of the starter motor. Thereafter, the voltage value Vh reaches the minimum value at time t3. When the voltage value Vh reaches the lower limit value VNL at time t4, the start control apparatus permits operation of the starter motor.
As described above, when the voltage value Vh becomes less than the lower limit value VNL, even if the shift lever is in a position corresponding to an engine start range, it may be determined that an engine start range is not selected, and operation of the starter motor is prohibited.